Gas-engine piston.



L. R. PRIEST,

sAs ENGINE PISTON. APPLICATION FILED FEB. 8. 19]].

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Patented Jan. 22, 1918.

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LESLIE R. PRIEST, OF OAND, GALIF'QENIA.

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Specification of Letters Fatent. Patented} Jam, {2 12, 1931a.

Application filed February 8, 191?. Serial lto. 147,312.

to minimize the vibration caused by the movements of the reciprocating parts, namely the pistons'and connecting rods, and, therefore, to obtain the maximum efliciency from the engine, it is highly desirable to make such parts as light as is consistent with the requisite amount of strength. Heretofore pistons have been made almost universally of castiron, for the reason that this material not only has sufiicient hardness to prevent excessive wear, but also expands and contracts, with changes of temperature, at

approximately the same rate as the cylinden wall, thus preserving, under all conditions, a proper running [it between piston and cylinder.

Cast iron pistons are necessarily heavy, however, and therefore cast aluminum has come into limited use. New aluminum has the disadvantages, first of havinga much greater coeflicient of expansion than iron, so that an aluminum piston must be-a comparatively loose fit in an iron cylinder; and second, aluminum, when raised to the working temperature of" a gas engine piston, wears very rapidly. Therefore, aluminum pistons must not only be loose at first, but this looseness rapidly increases as the engine is used. The serious disadvantages of a loose fitting piston are. too well require further elaboration.

The object of the present invention is to provide a piston, of the trunk type, which is light; which has approximately the same amount of expansion and contraction as the cylinder in which it operates; and whlch has.

sufiicient resistance to wear to insure a long life. A further object is to provide an improved means for supporting the wrist pin withinthe piston, so that the body or skirt of the piston is not distorted by the strains occasioned by the pressure upon said pin.

It is to be understood that the invention is herewith illustratedand hereinafter deknown to scribed in its preferred form, but that changes may be made in form and construction, within the scope of the claims hereto- X appended, without departing-from the spirit of the invention. With this in view, the:in-

vention is fully described with reference to the accompanying drawings, wherein Figure 1 is a part sectional :elevation' of my improved piston.

F ig. 2 is a part sectional elevation taken at right angles to Fig. 1. I

Fig. 3 is a part sectional plan, taken on the line 38 of Fig. '1, the; linesi11 and 22 indicating respectively the planes of Figs. 1 and 2. 7

Fig. 4. is a sectional elevation of a portion of a modified form of my piston;

Referring more particularly to the drawings, the reference numeral l designates the piston head, which is preferably cast of aluminum "or an alloy thereof, for the sake of lightness. This head has a rim 2 of sulficient width to accommodate packing rings 3, here shown to the number of two. At this portion, the rim 2 is made of a diameter to provide as close a fit as possible in the cylinder,-a llowing for the 'difierent amounts of expansion between the piston and the cylinder.

Below the packing ring portion 2 is a portion 4 of reduced diameter, formed upon its exterior surface with a screw thread, as

shown at 5. The skirt of the-piston is formed preferably of a seamlesscylinder 6 of steel or similar material, reinforced at its upper end by an interior ring 7, the latter being permanently secured to said skirt 6 throughout its entire circumference, as-by welding or brazing, and formed interiorly with a screw thread adapted to coact with the thread 5 upon the piston head flange 4.

The end of the skirt 6 is lineally slotted,

as. at 8, said slots extending transversely through the ring 7. Theseslots are provided for the: purpose of allowing the head and the skirt to have" unequal expansion, withoutlobseningthe joint, In addition to the screw threads 5, the skirt 6 is held upon the head l'by a series of rivets 9, one bei tween each pairof adjacent slots 8, and passing through the skirt, the ring 7, and

the head flange 4.

The piston pin, not shown in the drawings. is carried by bosses 10'projectin downwardly from the head1, and preferanly' cast integrally therewith Thus the piston pin is entirely within the skirt 6, being placed therein through a hole 6 inv said skirt; and the thrust of the pin is carried directly to the head 1, and any distortion caused thereby cannot afi'ect the skirt 6. v

The skirt 6, of course, forms the guide for the piston, and takes the entire wear caused by its travel within the cylinder. Said skirt, being made of iron or steel, can be made a close tit within the cylinder, without danger of binding when hot. The upper end of said skirt, where it is slotted and fastened to the head flange 4, is contracted sufiiciently to allow for the greater expansion of the aluminum head, but this difference in diameter, being necessarily small, does not appear in the drawings. Moreover, by making the head of aluminum or an alloy thereof, and the skirt of steel, as shown in Figs. 1, 2 and 3, a very light piston is obtained, which possesses all the advantages of an iron piston in regard to strength and wearing qualities.

The skirt may be made of cast iron, as

shown at 6 in Fig. 4. In this case the reinforcing ring is eliminated, the upper end of the skirt being made thicker, as at 7, and screwed directly onto the head flange 4, as at 5. Said skirt is slotted at its upper end, as indicated by the dotted line 8', and is additionally secured to the head flange 4 by rivets 9, in a manner identical with that described above. The cast iron skirt provides a cheaper, though slightly heavier construction than the steel skirt.

I claim '1. A piston comprising a head portion of relatively light metal; an independent skirt portion of a relatively hard, wear-resisting metal having a coeflicient of expansion different from that of the head portion metal; and means joining said portions adapted to permit their unequal expansion.

2. A piston comprising a head portion of relatively light metal, such as aluminum; an independent skirt portion of a relatively hard, wear-resisting metal, such as iron; and means joining said portions adapted to permit their unequal expansion.

3. A piston comprisinga head member of relatively light metal, formed with a journal boss extending inwardly therefrom; an

independent skirt portion of a relatively hard, wear resisting metal having a coefiicient of expansion diflerent from that of the head portion metal, said skirt portion sur- 4:. A piston comprising a head portion formed of aluminum, a cylindrical skirt portion formed of iron and having a series of slots extending downwardly from its upper end, and means for securing the slotted end of said skirt to said head.

5. A piston comprising a head portion provided with annular circumferential grooves; packing rings positioned within said grooves; a cylindrical flange of less diameter than said grooved portion and extending downwardly therefrom; a pair of spaced journal bosses extending downwardly from said flange; a skirt portion, of substantially the same diameter as the grooved portion of said head, adapted to surround said bosses in spaced relation and to fit over said flange; said skirt being provided with a series of spaced lineally disposed slots extending downwardly from its upper end; inter-engaglng screw threads formed upon the exterior of said flange and the interior of the slotted end of said skirt; and means for additionally securing said skirt upon said flange.

6. A piston comprising a head portionfa cylindrical skirt portion associated therewith, said skirt portion being formed upon one end with a plurality of longitudinally directed tongues, and means for independently securing each of said tongues to said head, to permit said skirt and said head to have unequal expansion and contraction.

7. A piston comprising a head portion formed of a relatively light metal such as aluminum; a cylindrical skirt portion associated therewith, said skirt portion being formed of a relatively hard, wear-resisting metal such as iron and provided upon one end with a plurality of longitudinally directed tongues; and means for independently securing each of said tongues to said head to permit said skirt and said head to have unequal expansion and contraction.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

LESLIE R. PRIEST.

Witnesses WM. F. Boorn, D. B. RICHARDS. 

